As mobile devices have been increasingly developed, and the demand of such mobile devices has increased, the demand of secondary batteries has also sharply increased. Among them is a lithium secondary battery having high energy density and voltage and excellent preservation and service-life characteristics, which has been widely used as an energy source for various electronic products as well as the mobile devices.
On the other hand, various kinds of combustible materials are contained in the lithium secondary battery. As a result, the lithium secondary battery may be heated or explode due to the overcharge of the battery, the overcurrent in the battery, or other physical external impacts. That is, the safety of the lithium secondary battery is very low. Consequently, the lithium secondary battery includes a protection circuit module (PCM), which is connected to the battery cell for effectively controlling an abnormal state of the battery, such as the overcharge of the battery.
Generally, the PCM is connected to the battery cell using a conductive material, such as a nickel plate, by welding or soldering, which increases a coupling force between the PCM and the battery cell. However, the welding or soldering process requires a high degree of technical skill, with the result that skilled persons are needed. Also, the welding or soldering process requires a large working space. Furthermore, when physical impacts are applied to the battery cell, electrical shorts may occur, and therefore, the battery cell may catch fire or explode. In other words, safety-related problems may occur.
Consequently, research on various technologies that are capable of complementing drawbacks of the welding or soldering process, while maintaining advantages of the welding or soldering process, is being actively pursued. For example, Japanese Patent Application Publication No. 2004-335387 discloses a structure in which a circuit board block, which is integrated with a circuit board, is provided at opposite ends thereof with through-holes, rod-shaped connecting members, which are made of a metal material, are inserted through the corresponding through-holes, such that the connecting members are brought into contact with the top of a battery cell, and the connecting members are coupled to the top of the battery cell by resistance welding.
However, the above-described technology has a problem in that the welding process is still used to couple the rod-shaped connecting members to the top of the battery cell, and therefore, the manufacturing process is difficult, and the safety of the battery cell is still low.
Also, Japanese Patent Application Publication No. 2006-147193 discloses a structure in which a battery case is provided at the top thereof with a female type coupling structure, a plate-shaped protection circuit board is provided at opposite sides thereof with through-holes, a battery pack cover is also provided at opposite sides thereof with through-holes, screws are threadedly inserted into the female type coupling structure of the battery case through the through-holes, while the protection circuit board is placed on the top of the battery case, and the battery pack cover is mounted to the top of the battery case. Japanese Patent Application Publication No. 2006-04783 discloses a structure in which coupling protrusions are formed at the top of a battery cell by welding, a battery pack cover is provided with female type coupling members corresponding the coupling protrusions, and the battery pack cover is coupled to the battery cell by forcibly inserting the coupling protrusions into the corresponding female type coupling members.
However, the above-described technologies have a problem in that an additional coupling structure is formed at the top of the battery cell, which is very troublesome. Especially for the latter case, the protrusion type coupling structure is formed at the top of the battery cell, and, a welding process is used to form the protrusion type coupling structure, whereby the manufacturing process is difficult, and the safety of the battery cell is still low.
Also, Japanese Patent Application Publication No. 2006-164531 discloses a battery pack including a battery cell, a circuit board mounted to the top of the battery cell, and an upper case, wherein the upper case is fixed to the top of the battery cell by threadedly inserting screws into coupling grooves formed at the top of the battery cell through through-holes formed through the upper case. Korean Patent Application Publication No. 2006-32591 discloses a secondary battery constructed in a structure in which an upper cover is mounted to the top of a battery core, while a structure supporting member for supporting a protection circuit board is inserted, the battery core is provided at the top thereof with position holes and screw holes, the upper cover is provided at the bottom thereof with position notches and screw openings, and the upper cover is coupled to the top of the battery core by engaging the position notches into the corresponding position holes and threadedly inserting screws into the screw holes through the screw openings.
However, the above-described technologies have problems in that an additional member is inserted between terminals of the battery cell and the protection circuit board for accomplishing the electrical insulation between the terminals of the battery cell and the protection circuit board, and it is required to provide additional connecting members, such as connection pins, for the electrical connection with the electrode terminals, whereby the assembly process is complicated. Especially for the latter case, the connecting members may be easily separated from the electrode terminals, with the result that an external short circuit may occur, and the battery pack may become defective during the handling and manufacture of the battery pack. Such additional provision of the insulative/conductive members complicates the assembly process. Also, the manufacturing process is very complicated, and the safety of the battery cell is deteriorated, when the welding process is used. Furthermore, the screws necessary for the coupling are partially exposed to the outside, with the result that a possibility of a short circuit occurring is increased. In addition, the battery does not exhibit a pleasing aesthetic appearance, which acts as a deterring factor when consumers choose products.
Consequently, there is a high necessity for a technology that is capable of reducing the number of members mounted to the top of the battery cell to simplify the assembly process and securing no-welding type stable coupling strength between the battery cell and the mounting members.